Testosterone undecanoate, known as ANDRIOL, has been marketed in many countries for male hypogonadism, since 1978. The first ANDRIOL market formulation was a digestible formulation containing oleic acid. The drawback of this formulation is that it only had a shelf-life of three months at room temperature. The short shelf-life was caused by reesterification of the undecanoate ester with oleic acid. Due to this instability, a new formulation containing castor oil and lauroglycol was developed.
This new formulation is disclosed in U.S. Pat. No. 6,652,880 and US Application No. US2005/0287203 and has been on the market in many countries as ANDRIOL TESTOCAPSS since 2003. The ANDRIOL TESTOCAPS formulation is a non-digestible formulation with a shelf-life of 3 years.
Testosterone undecanoate has a Log P of 9.1 and very low water solubility. Both ANDRIOL and ANDRIOL TESTOCAPS formulations show an absolute bioavailability of 4% in fed state. Together with a medium to high fat meal, testosterone undecanoate is emulgated in the gastrointestinal tract through a combination of digested fats and bile acids. Once emulgated, testosterone undecanoate is incorporated into the chylomicrons and absorbed via the lymph. In fasted state no elevated testosterone undecanoate and/or testosterone serum levels are obtained. Thus, there is still a need for a stable, preferably low-dose pharmaceutical formulation of testosterone undecanoate that results in increased exposure and a decreased food-effect so that patients can rely on testosterone undecanoate being absorbed in fasted state as well as with low-fat meals.
Self-emulsifying formulations of testosterone esters are described in several U.S. patents and applications including: U.S. Pat. No. 8,241,664, which describes a self-emulsifying drug delivery system (SEDDS) of testosterone undecanoate using digestible oils, hydrophilic surfactants, and hydrophobic surfactants; U.S. Patent Application Publication No. 2011/0251167 which describes preparation of SEDDS of testosterone undecanoate containing oleic acid, CREMOPHORE RH40, peppermint oil and borage oil; U.S. Patent Application Publication No. 2012/0135069 which describes preparation of nanonized testosterone esters using solid lipid matrix (stearic acid); U.S. Patent Application 2012/0135074 and 2012/0148675 which describe compositions of testosterone undecanoate in various solubilizers to achieve a concentration of testosterone undecanoate of 14-35% as a solution, mixture of crystalline and solution, and a solid mixture; and U.S. Patent Application No. 20130303495 which describes an emulsion, microemulsion or nanoemulsion formulation for pharmaceutical administration of testosterone undecanoate comprising a digestible lipid, a water-soluble surfactant, a water-insoluble surfactant; a phytosterol and/or phytosterol fatty acid esters, and dl-alpha-tocopherol. However, such formulations do not all achieve a stable, preferably low-dose pharmaceutical formulation of testosterone undecanoate that results in increased exposure and a decreased food-effect so that patients can rely on testosterone undecanoate being absorbed in a fasted state as well as with low-fat meals.